Unique renal histopathological appearances, consisting of podocytic infolding and microstructures in the glomerular basement membrane (GBM) were identified in the renal biopsies from three patients with collagen diseases such as systemic lupus erythematosus (lupus nephritis, class II) and Sjögren's syndrome. In each case, the GBM contained microstructures, including microspheres and microtubular structures, accompanied by podocytic infolding into the GBM when examined by electron microscope. The size of the microstructures in the GBM ranged from 40 to 160 nm. Glomerular endothelial cells also seemed to be infolded in the GBM in a case with lupus nephritis. The response to glucocorticoid therapy was favorable in two cases. The cause of these morphological changes in the GBM might be associated with autoimmune disorders.